In U.S. politics and government, caucus has several distinct but interrelated meanings. One is frequently used to discuss the caucuses used by some states to select presidential nominees, such as the Iowa caucuses.

...bottom line is that a Caucus is merely an old word for a meeting or session that is necessary to establish the credentials of the presidential nominees, similar to the primaries. It's mostly semantics for what you and I, and other average voters need to know. This is basically "game time" for the candidates to prove why they are more prepared to be President than the person standing next to them.

If a nominee "wins" the Caucus in the Iowa voters' minds, they are therefore rocketed ahead of the pack. Think of NASCAR. The more races you win, the more points you get, which puts you in line to win the championship. Winning each race proves that you are the fastest and best on the track. That is the purpose of the caucus and primaries...to prove that you are deserving of the vote of the population of that state.

By the way, I don't watch NASCAR but I did read a NASCAR magazine last week.

Also, if you win a Caucus and some Primaries you are proving your credentials to your respective party. If you win the Caucus you'll more than likely (historically) win your party's nomination. So whoever wins the Caucus on 3 January, 2008 for each party will most likely be your next presidential candidates to vote for in November.

The Iowa Caucus: Free information directory for the presidential election 2008 in Iowa. Caucuses Polls, History & candidates.